Impact of Biomass Burning Plumes on Photolysis Rates and Ozone Formation at the Mount Bachelor Observatory

Abstract

In this paper, we examine biomass burning (BB) events at the Mt. Bachelor Observatory (MBO) during the summer of 2015. We explored the photochemical environment in these BB plumes, which remains poorly understood. Because we are interested in understanding the effect of aerosols only (as opposed to the combined effect of aerosols and clouds), we carefully selected three cloud‐free days in August and investigate the photochemistry in these plumes. At local midday (solar zenith angle (SZA) = 35°), j(NO2) values were slightly higher (0.2–1.8%) in the smoky days compared to the smoke‐free day, presumably due to enhanced scattering by the smoke aerosols. At higher SZA (70°), BB aerosols decrease j(NO2) by 14–21%. We also observe a greater decrease in the actinic flux at 310–350 nm, compared to 360–420 nm, presumably due to absorption in the UV by brown carbon. We compare our measurements with results from the Tropospheric Ultraviolet‐Visible v.5.2 model. As expected, we find a good agreement (to within 6%) during cloud‐free conditions. Finally, we use the extended Leighton relationship and a photochemical model (Aerosol Simulation Program v.2.1) to estimate midday HO2 and RO2 concentrations and ozone production rates (P(O3)) in the fire plumes. We observe that Leighton‐derived HO2 and RO2 values (49–185 pptv) and instantaneous P(O3) (2.0–3.6 ppbv/h) are higher than the results from the photochemical model.

Transport of Central American Fire Emissions to the U.S. Gulf Coast: Climatological Pathways and Impacts on Ozone and PM2.5

“…The compositing approach does not examine the case‐by‐case variability. Therefore, we do not explicitly examine other internal factors affecting the fire impact on air quality, such as the chemical evolution of fire‐emitted species and ozone precursors during the course of the plume transport and mixture of the fire emissions with urban pollution (Baylon et al, ). Future work is needed to improve our understanding of these aspects, which would require in situ measurements of the fire plumes as well as detailed modeling of the plume chemistry and small‐scale transport.…”

Potential link between compromised air quality and transmission of the novel corona virus (SARS-CoV-2) in affected areas

“…Increasing numbers of vehicles on the national highways provide three-dimensional corridors of smoke which contains oxides of nitrogen and black carbon. Subsequently, ground level ozone (O 3 ) is produced as a result of the photolysis of oxides of nitrogen by wavelengths less than 420 nm present in solar radiation in a rich environment of VOCs (Baylon et al, 2018), which is one of the primary species that can initiate Chronic Obstructive Pulmonary Disease (COPD) and Asthma due to its strong oxidative capacity. Thus, the possibility of COVID-19 susceptibility is much higher in those who are already exposed to oxidants in polluted areas.…”

Simulating the forest fire plume dispersion, chemistry, and aerosol formation using SAM-ASP version 1.0

“…In addition to the pollutants directly emitted by fires, chemistry in smoke plumes can produce ozone (O 3 ), which can negatively impact human health (U.S. EPA, 2013) as well as affect vegetation, water quality, soil, and the ecosystems that they support (European Environmental Agency, 2018). O 3 formation can occur due to the emission of nitrogen dioxide (NO 2 ), HONO, and volatile organic compounds (VOCs) and the presence of sunlight (Baylon et al, 2018), with enhanced photolysis rates occurring most predominantly during midday, when photolysis rates are fastest. In 2012, the estimated median contribution of fires to maximum daily 8 h average (MDA8) O 3 in Texas during the month of June was 2 ppbv, with maximum impacts of over 40 ppbv (McDonald-Buller et al, 2015).…”

“…Large uncertainties exist, however, in quantifying O 3 production, which stems from uncertainties in fire emissions, combustion efficiency, meteorological patterns, chemical and photochemical reactions, and the effects of aerosols on plume chemistry and photolysis rates. Aerosols have been shown to both increase O 3 formation (e.g., scattering particles can increase photolysis rates) as well as decrease O 3 (absorbing aerosol and black carbon-containing aerosol can reduce photolysis rates) (Baylon et al, 2018). Hence, the aerosol composition and size distribution, which varies within and between plumes (Collier et al, 2016), and the location of the aerosol within the plume (Alvarado et al, 2015) impact O 3 production.…”